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'Carbon Trees' Would Suck CO2 Out of Air and Into Your Soda

Carbon trees computer rendering
A computer rendering of synthetic trees that capture CO2 out of the air.
New devices could capture greenhouse gas and provide CO2 for commercial uses, all in one pop

Carbon dioxide is one of the most plentiful gases in the atmosphere, but when soda makers want to inject the fizz into their sweet-tasting drinks, they often have to pay through the nose for it. Many bottlers buy CO2 that was created as a byproduct of industrial processes, paying up to $300 per ton for the gas.

So what if instead of relying on CO2 shipped via tanker trucks, soda makers could snare the gas right out of the air with a forest of roof-mounted synthetic "trees" -- cutting their costs and helping reduce greenhouse gas pollution at the same time?

That's the vision of Billy Gridley, CEO of Global Research Technologies (GRT), a New York-based startup that is working to make prototypes of these high-tech devices commercially viable. Not long ago, few scientists believed it was possible to extract CO2 out of the atmosphere in a way that could be profitable. The barrier? Most methods of CO2 extraction consume enormous amounts of energy and require trucks or pipelines to ship the CO2 where it's needed, which gets prohibitively expensive.

GRT sees a way around those problems: create a device to capture the CO2 where it's needed. The company has devised a lower-energy approach that Gridley says can capture CO2 cheaply enough to supply commercial buyers of the gas. The devices are called "carbon trees" because they mimic the carbon dioxide-absorbing abilities of real trees. In time, Gridley believes, GRT's technology will be ready to help meet the huge challenge if Congress or the Environmental Protection Agency dictate that CO2 emissions must be captured and stored permanently as a potential solution to climate change. 

Air capture demo systemFor now, GRT's breakthrough looks less like a tall tree than a single fuzzy branch, one that's connected to hodgepodge of tubes, compressors and other gizmos. GRT unveiled a working demonstration setup at last December's meeting of the American Geophysical Union in San Francisco. By proving the viability of its technology, GRT created hope in climate science circles that "air capture" could yet emerge as a viable economic option to reduce global warming pollution. 

Above: GRT demonstrated its air capture technology at the American Geophysical Union conference last December. Photo: Molly Samuel, KQED.org

Their prototype stands out because today no other system is being commercialized to capture CO2 out of ambient air. Others are focusing instead on industrial emissions. Backed by billions in public subsidies, engineering leaders such as Alstom, GE, and Siemens are racing to standardize systems that can snare the greenhouse gas exhaust from cement kilns, steel mills, and power plants, where CO2 levels are much higher than in the atmosphere. More than half of global greenhouse gas emissions come from such "stationary" sources.  

Utility executives describe the challenge of developing these systems as something like retrofitting a chemical plant on the back of a power plant. And once captured from power plants and factories, the CO2 will have to be trucked or piped away, either to markets where it can be sold, or to geological formations where it can be buried. Creating such a CO2 network, critics argue, will be on par with replicating the nation's natural gas pipeline system -- a 213,000-mile-long network built over the span of a century.

GRT's approach promises to eliminate much of this costly distribution infrastructure. Consider a McDonald's today. "To carbonate beverages at the soda fountain, every week or so a truck rolls up to refill their CO2 supply," says Gridley. "A GRT unit (on the roof of the restaurant) could eliminate all those trucks, and all the fuel needed to deliver the CO2."

The seed of GRT's project to build synthetic trees took root in 2004, as a breakthrough made by Klaus Lackner, a geophysicist at Columbia University. Conventional CO2-capturing approaches rely on some combination of chemical additives, heat, and pressure to process CO2. But Lackner began toying with a class of materials that he knew had a chemical propensity to lock up CO2 on their surface.

Lackner's insight was part luck, part hunch. The twist was realizing that an increase in humidity -- rather than energy-hogging shifts in heat or pressure -- could get the material to exhale its captured CO2. "I didn't quite believe it when I got it to work the first time," he says. Another cost-savings plus: the material Lackner identified is commonly available as a resin, or plastic, that can perform thousands of capture-and-release cycles.

"Carbon tree" carouselGRT's first commercial version will look more like a merry-go-round than a tree. The entire device is designed to be packed into a standard shipping container, making it easy to transport. When set up, door-sized panels made of Lackner's special resin are hung on a carousel that will rotate slowly, exposing them to CO2 as they go round. Upon completing a revolution, a panel is automatically retrieved from the carousel and pulled into a chamber where it is wetted to release the stored CO2.  The filter is then returned to the carousel for another rotation.

Above: Artist's rendering of commercial air capture system. Courtesy GRT

The process generates a stream of "dilute CO2," as much as 250 times more concentrated than in the atmosphere, at concentrations of about 5 to 10 percent. To generate pure CO2, the panels can be wetted in a vacuum -- a step that can double or triple adds costs.

Someday, Lackner imagines, this extraction step could be performed inside tree-like towers designed to automatically seal, extract the CO2, and then reopen once the gas is piped away.  "The taller the structures are, and the more surface area they have, the more CO2 they'll capture," says Lackner.

First on GRT's hit list of potential customers are those with an appetite for dilute CO2: agricultural and biofuel players such as greenhouses and algae farms, which need large volumes of dilute CO2 to feed to their plants. Algae farms are emerging as a source of renewable biofuels, such as bio-diesel or "green gasoline." In these markets, GRT anticipates selling dilute CO2 at $50 to $75 per ton. (In December, as part of $564 million grant for biofuels development, the U.S. Energy Department directed $125 million to five algal-fuel projects). 

GRT's other early-stage target includes the $1-2 billion market for pure CO2, such as producers of carbonated drinks and dry ice. Trucking costs can drive up prices for pure CO2 to $300 per ton for customers the farthest away from the source.  In both these arenas, GRT plans to deliver cost-competitive CO2 by 2012.

GRT's next step would be to sell to very-high volume buyers. Today's biggest market for CO2 is in the United States' "oil patch," where drillers pump liquefied CO2 under high pressure into aging wells to drive more oil out of them. In Texas and the Southwest, the center of this "enhanced oil recovery" industry, drillers tap into natural reservoirs of CO2 in the earth and ship them to oil fields via pipeline. It's roughly a $10 billion market today, where some 40 million tons of pure CO2 is bought annually. As the price of oil goes up, the thirst for CO2 rises; even at current prices, today's CO2 supplies can't meet demand. Gridley figures that if GRT can drive down its costs to $50 per ton of pure CO2, demand from oil drillers could be worth tens of billions of dollars annually.

All this depends, of course, on whether GRT can successfully drive down the price of its systems. Standardizing the design is the key to reducing costs. 

"It's like manufacturing cars," says Lackner. "Build one by hand, and it's expensive. But build thousands on an assembly line, and the per-unit cost falls dramatically." Today, as GRT debugs its prototype to launch one-off mobile units next year, Lackner estimates the price for a single rig would be around $200,000. If GRT can scale up to supply the oil patch markets, he predicts large-scale manufacturing would drive the price down to a car-like $20,000 per unit.

Farther out, the biggest opportunity of all for carbon capture players could be U.S. or global carbon markets. By 2020, if Kyoto-style regulations to control greenhouse gas pollution are adopted in the United States, Gridley estimates that some 2,000 million tons of CO2 would have to be captured and sequestered annually -- potentially a $40 billion business. By that time, Gridley hopes GRT's air capture technology will be among the lowest-cost options for companies looking to meet the new rules.

But the company must first prove that it can supply today's soda makers with something closer to one ton per day. In the past year, GRT relocated from Arizona to New York City, where Lackner is building a research team at Columbia University to advance the basic science of air-capture technology.

Gridley, meanwhile, is focusing on developing and contracting out the company's first fully-integrated prototype. He's also hunting for venture capital to fund commercial development of the company's first round of commercial units, scheduled to roll out in 2011.

image of Adam Aston
Adam Aston is a freelance journalist and editor who focuses on green issues. Previously, Adam was energy and environment editor at BusinessWeek, where he covered corporate sustainability, renewable energy, and green finance while producing a regular ... READ MORE >

This is fascinating. I knew that smokestack scrubbers was a viable possibility for extracting CO2 but had no inkling of anything like this. I'm really enjoying your writing on environmental issues.

Vaporware.

Okay, yeah, let's attempt to use technology to suck a gas that's necessary for plant life right out of the atmosphere. We're totally the most responsible creatures, so we know how to implement this without disaster.

actually Co2 is NOT one of the most common gases in the atmosphere. At 380 ppm, it ranks well behind nitrogen, oxygen, argon, and water vapor.

You would think that a science writer would know that Carbon dioxide is NOT one of the most plentiful gases in the atmosphere but a trace gas. Welcome to the new world of 'climate science.
And well ahead of many others, including methane, carbon monoxide, nitrous oxide, and a bunch more. Let's agree it makes the top five and move on, shall we?

Solutions like this absolutely drive me wild...

Instead of building more ugly things to stick onto our landscapes to try to reverse our pollution-minded ways, let's direct our energies towards making LESS pollution in the first place!

To frank: Haven't you been following the news? Human activity (fossil fuel burning)is pouring 10 billion tons of CO2 into the atmosphere each year. The demand for commercial c02 is a tiny fraction of this. I don't know of anyone who thinks there is to little c02 in the atmosphere.

If you don't know anyone who thinks there is to little CO2 in the atmosphere, you haven't talked to any one who runs a commercial greenhouse, and you don't know that current levels of CO2 are low by the standards of geological time.

It is always amusing to see computer renderings and articles on concepts and hunches (as mentioned in the article itself)- claiming to solve big problems.

I strongly recommend that we stop distracting ourselves with notions of fantasy and solve some real issues such as poverty, global hunger and disease.

Sadly, nearly twenty years of largely futile effort to significantly mitigate global CO2 emissions suggests that we are going to need to deploy "geo-engineering" solutions in order to avoid the worst effects of global climate change, whether we like the idea or not. Obviously, changing our polluting ways would be the best thing, but it doesn't look as if we are going to do enough soon enough--although we could have, if we hadn't gotten caught up in propaganda on the topic. I, for one, would prefer more carbon capture, and less in the way of most other "geo-engineering" interventions that have been proposed. Some proposals include fertilizing the oceans to stimulate bio-capture of CO2 by algae, soil sequestration of CO2 by creation of biochar, re-forestation, and various schemes to manipulate Earth's albedo (including painting roofs white, shielding Polar ice, placing special mirrors in orbit, and injecting sulphuric acid aerosols into the stratosphere.)